Capital appreciation in good markets far outstrips any income gains one can make but it is volatile.

There is huge volatility in the quality level of bookkeepers.

It’s a volatile situation every time you rent to someone.

The Phoenix market was too volatile and risky for me to feel comfortable around this time and there were no real duplexes there, so I convinced my husband to move to Rochester, NY where multi-families are everywhere and we could live super cheap.

So I read the the very well written copy full of pressure on the pain points of being a dentist, investing in the volatile stock market, multiple testimonials, and a compelling call to action from a client rather than Phelps!!!!

Remember, this is a local real estate play and spreading your investments across a few areas to build multifamily will grant you better protection from market volatility.

Or sell those and place it into less volatile real estate that you have more control over. 

Broadly for me/us I'd just say that our perception of where the market/economy is headed just informs more of a general intuitive appetite for using leverage.My view is that uncertainty in future market outlook (perhaps forecasted by leading indicators) mainly drives price volatility, and perhaps increases risk of lenders 'calling' revolving credit lines to meet their own liquidity needs.The more 'bad' the indicators are, the more chance that we perceive our lenders possibly wanting to 'call' revolving lines of credit, is the way I think about it.  

Covid run up on prices made this area volatile in the short term.

To your final question: crypto is very volatile, yes.